During a specific surgical operation or some other procedure requiring oral or nasal endotracheal intubation, one or more endotracheal tubes are inserted into a patient via the mouth and throat or nose and throat of the patient, to facilitate positive pressure ventilation to and from the patient's lungs during the surgery. The technique of orotracheal or direct nasaltracheal intubation involves sighting the insertion of the endotracheal tube into the throat of an anesthesized patient. A variety of equipment may be used for this technique, but always including a proper sized endotracheal tube or tubes, a functioning laryngoscope, and appropriate anesthetic drugs and neuromuscular blockers. After the tube is inserted there must be, of course, facilities to provide the positive pressure, oxygen ventilation.
Training and experience contribute to making the technique safe, effective, and atraumatic. For example, a safe approach to a surgical procedure involves first providing the patient with a barbituate and a skeletal muscle relaxant before initiating laryngoscopy. Then the head, neck, and shoulders of the patient must be positioned so that the oral, pharyngeal, and laryngeal axes are aligned. Finally, the laryngoscope is inserted, preferably with the laryngoscopist's left hand--without regard to whether the laryngoscopist is right or left handed--on the right side of the patient's mouth to avoid the incisor teeth and to deflect the tongue away from the lumen of the laryngoscope blade. The laryngoscopist sights the epiglottis above the base of the tongue and, according to the type of laryngoscope blade used, manipulates the instrument to expose the glottis opening.
There are many types of laryngoscope blades, each characterized by the blade curvature or lack thereof, the point of such curvature if the blade is curved, and the flange structure of the blade. Three types of blades are most prominently used. A first type of blade, characterized as a curved blade, is known in the art as the Macintosh blade. This type of blade is advanced into the space between the base of the tongue and the pharyngeal surface of the epiglottis. Forward and upward movement of this blade stretches the hypoepiglottic ligament to cause the epiglottis to move upward to expose the glottic opening. Two other types of prominently used blades are the straight blade, known as the Jackson or Wisconsin blade, and the straight blade with a curved tip, known in the art as the Miller blade. The tip of these blades are passed beneath the laryngeal surface of the epiglottis and moved upwardly to elevate the epiglottis, thereby exposing the glottic opening.
During insertion of the laryngoscope, care must be taken to avoid pressure on the teeth and gums of the patient. Care must also be taken to avoid traumatizing the oral mucosa and to avoid bruising the epiglottis. By using a gentle technique for inserting the laryngoscope, the laryngoscopist might lessen the possibility of such trauma. But choice of instrumentation might also lessen trauma. For example, less trauma to the teeth is associated with a curved blade, and because the curved blade should not touch the epiglottis, there is less bruising of the epiglottis associated with use of the curved blade. Another trauma lessening instrument is a protective shield that might be placed over the maxillary incisors.
These methods and instrumentation have limited advantage. No matter how gentle the insertion, the manipulation to expose the glottic opening is an invasive technique whereby the hard edge of the blade scrapes against the oral mucosa when manipulated to open the glottis. Whatever advantages are associated with use of the curved blade, there are also advantages to use of the straight blade, and its choice is often the result of personal preference by the laryngoscopist. Even the protected shield has limited advantage, as it only protects the teeth and not the tongue and oral mucosa.